Histamine, Serotonin, Antacids... Flashcards
Does histamine cross the blood brain barrier?
No
What are the effects of histamine on H1 receptors?
REspiratory and GI smooth muscle contraction
Pruritis/sneezing
NO release by vascular smooth muscle
What are the effects of histamine bound to H2 receptor?
Increased GI secretion of H+
Increased HR/contractility
What is the effect of histamine on the H3 receptor?
decreased histamine synthesis and release
What are 5 generalized effects of histamine?
Dilation of arterioles and capillaries flushing decreased systemic vascular resistance decreased BP increased Capillary permeability
H1 activation occurs at higher concentratrations of histamine than H2. T or F
false
H1 activation occurs at lower concentrations
T/F H1 activation decreases AV Node conduction
true
H1 activation causes coronary artery _________ while H2 activation causes coronary artery ______________
vasoconstriction
vasodilation
How does H2 activation affect the heart?
Causes catecholamine release from adrenal medulla
increases HR and contractility
coronary artery vasodilation
How does the skin respond to histamine?
dilated capillaries in affected area
Edema-increased capillary permeability
Wheal-dilated arteriols around edema
How do histamine antagonists work to treat allergic reaction?
block edema and pruritis but don’t block hypotension–give epi
t/f Histamine blockers act on both H1 and H2 receptors , are competitive inhibitors and are well absorbed orally.
F–act on one receptor or the other, not both
What is the difference in first and second generation H1 blockers?
First generation also activate muscarinic cholinergic, serotonin and alpha receptors and can cause significant sedation.
Second generation H1 blockers act only on H1 receptors and cause much less sedation
At high doses Second generation H1 receptors may become ______________
non-competitive
What are side effects of first generation H1 blockers?
Somnolence Decreased alertness slowed rxn time Dry mouth Blurred vision urinary retention impotence tachycardia Dysrythmias
What are teh side effects of second generation H1 blockers?
Q-T prolongation at high doses
What are clinical uses for H1 blockers?
Rhinoconjuctivitis
Bronchospasm (pretreat)
Anaphylactic/anaphylactoid rxns
motion sickness
Name 4 H2 blockers and their potency
Cimetidine (tagamet) potency=1
ranitidine (zantac) potency = 10
famotidine (pepcid) potency = 50
Nizatidine (Axid) potency=10
H2 blockers are rapidly absorbed orally, have minimal first pass metabolism, and cross both BBB and placenta. T/F
False. These drugs have extensive first pass metabolism and therefore are given at high doses
How are H2 blockers affected by pts with renal dysfunction
extends half life of drugs, so you shoud decrease the dose
What are clinical uses of H2 blockers
Treatment of duodenal ulcers
Allergy prophylaxis
Pre op med
What effects do H2 blockers have when given preop?
decrease gastric volume
INcrease gastric pH
What are most common H2 blocker side effects?
diarrhea
headache
fatigue
malaise
Prolonged use of H2 blockers may ______ gastric barrier to bacteria
weaken
Which H2 blocker binds and inhibits cytochrome p450?
cimetidine–It may also delay clearance of lidocaine due to a decrease in hepatic blood flow
How does cromolyn affect histamine? How is it used?
Inhibits antigen-induced release of histamine from mast cells
Used as a phrophylaxis for bronchial asthma and is administered by inhalation
What type of drugs are omeprazole, protonix and prevacid?
H+ pump inhibitors
How do H+ pump inhibitors compare to H2 inhibitors?
Work longer (up to 24 hours) and give better results than H2 blockers
How are H+ pump inhibitors used for anesthesia?
as a pre op medicine they increase gastric pH, decrease gastric fluid volume. They must be given > 3 hours prior to surgery
Serotonin causes vasoconstriction in _________, _________, and ___________
cerebral, coronary and pulmonary
90% of serotonin is found in enterochaffin cells of _________, the rest is in ________ and _________
GI tract
CNS and platelets
Serotonin is Oxidized by ___________ and ________, and taken up by _________
liver and lungs
platelets
What does 5 HT1 cause. What is a drug that agonizes these receptors?
Cerebral vasoconstriction
Sumatriptan (Imitrex) revers middle cerebral artery vasodilation and improves migraine and cluster headaches
How do 5HT2 antagonists work?
Kentanserin attenuates vasoconstriction, bronchoconstriction and platelet aggregation, and acts as an alpha blocker
What conditions may be treated by 5-HT3?
N/V
appetite
addiction
pain anxiety
How can you tell if a drug is a 5 HT3 antagonist?
ends in setron
What are side effects of Zofran?
headache
diarrhea
increased liver enzymes
How do antacids work?
acid+base=salt
at pH>5 pepsin is inactivated, LES tone is increased, and gastric contents are pushed forward
what are characteristics of sodium bicarbonate?
highly soluble
rapid action in stomach for a brief duration
May cause alkolosis
Avoid in renal and heart pts. May increase sodium load
Magnesium hydroxide can cause acid rebound, and has a laxative effect. t/f
false. no acid rebound
What may happen with high doses of magnesium hydroxide?
Neuro/NM effects
Calcium carbonate is rapidly absorbed, can cause and acid rebound, and may cause hpercalcemia and metabolic alkalosis with chronic use. t/f
true
how is aluminum hodroxide absorbed?
what may it deplete?
HOw does it affect gastric emptying?
Minimally
phosphate
decreased
How do antacids affect other drugs?
increased delivery of PO medicines but decreased bioavailability
Antacids decrease incidence fo regurgitation and aspiration. T/f
f. no effect
What is an example of an antacid that may be given pre op?
bicitra (sodium citrate and citric acid)
How does sucralfate work? what is it used for?
reacts with HCL in stomach to form a viscous paste which forms a protective barrier in stomach. Used to treat duodenal and stomach ulcers
What are the effects of metoclopramide?
increases gastric emptying
increase LES tone
Relaxes pylorus and duodenum when the stomach contracts
What are side effects of metoclopramide. Which pts should they be avoided in?
may cause sedation, agitation, and dysphoria -give slowly or post induction Most common -dry mouth -abdominal cramping -dysrhythmias -extrapyramidal effects Rare -Hirsutism -Macropapular rashn With chronic use there is a prolactin association leading to breast enlargement and menstrual irregularities Don't give to GI obstruction Since it is a dopamine antagonist it should be avoided in parkinsons pts
how is metoclopramide eliminated?
renally
What are clinical uses of metoclopromide?
pre-op adunct
anti-emetic
gastroparesis therapy
symptomatic GERD
Which patient needs metoclopramide?
full stomach trauma obese diabetic parturient
What are effects of Domperidone?
dopamine antagonist stimulates peristalsis increases LES tone Increase gastric emptying No cholinergic or central effects like reglan
What is cisapride (propulsin)?
How does it work?
gi Prokinetic
causes an increase in ACh and PS activity which increases gastric emptying. used for pts with gastroparesis
